Wind turbine nacelle

ABSTRACT

The present invention relates to a nacelle for a wind turbine, the nacelle having a first height in its installed position and a second height in its transported position, the first height being higher than the second height, comprising a bottom part having a bottom face and two opposite side faces defining a space and a width of the bottom part and a top part. In the transported position, the top part extends inside the width or outside the width in order to cover at least part of the space. The invention also relates to a transportation kit and a transport method.

FIELD OF THE INVENTION

The present invention relates to a nacelle for a wind turbine, thenacelle having a first height in its installed position and a secondheight in its transported position, the first height being higher thanthe second height, comprising a bottom part having a bottom face and twoopposite side faces defining a space and a width of the bottom part anda top part.

BACKGROUND ART

Transportation of large elements on a truck requires special transportequipment in order to adjust the truck to suit the particular element tobe transported. Furthermore, national regulations of a country or astate may require that the transport does not exceed a certain height ora certain weight.

In many countries in Europe and in USA, a certain overall height hasbeen specified which a truck including an element may not exceed. Inorder to comply with these regulations, special transport equipmentenabling the element to be transported on a platform lowered downbetween a front part of a truck and a rear part of a truck may berequired.

Even though the transport equipment is designed to minimise the overallheight, the overall height of the element and the transport equipmentmay for some elements, such as a large wind turbine nacelle, still betoo high. In such cases, the element has to be transported in two ormore parts and, thus, assembled when arriving at its destination.

SUMMARY OF THE INVENTION

An object of the present invention is, at least partly, to overcome theabove disadvantages and drawbacks of the prior art and to provide animproved nacelle for a wind turbine which is easier to transport, evenif the nacelle is a large nacelle.

The above object, together with numerous other objects, advantages, andfeatures, which will become evident from the below description, isaccomplished by a solution in accordance with the present invention by anacelle for a wind turbine having a first height in its installedposition and a second height in its transported position, the firstheight being higher than the second height, comprising a main framestructure, a bottom part connected to the main frame structure andhaving a bottom face and two opposite side faces defining a space and awidth of the bottom part and a top part, wherein the top part in thetransported position extends inside the width or outside the width inorder to cover at least part of the space.

In this way, the top part can be used to cover the bottom part duringtransport so as to prevent dirt etc. from entering the bottom part fromabove. In addition, no separate vehicle is needed to transport the toppart, as both the top part and the bottom part can be transported on onevehicle when the height of the nacelle is adjustable.

In one embodiment, the top part may comprise two parts which in thetransported position of the nacelle are separated from each other inorder for the top part to extend outside the width of the nacelle oroverlap each other in order for the top part to extend inside the widthof the nacelle.

It is thus not necessary to press the side faces towards or away fromeach other in order to minimise the height of the nacelle duringtransport. Furthermore, the top part does not get scratched duringinsertion of the top part between the side faces.

The top part may moreover comprise a top face and two intermediate partsintermediate the side faces and the top face, which two intermediateparts are dismounted in the transported position.

In an alternative solution according to the invention, the nacelle mayhave a first height in its installed position and a second height in itstransported position, the first height being higher than the secondheight, the nacelle comprising a main frame structure, a bottom partconnected to the main frame structure and having a bottom face and twoopposite side faces defining a space and a width of the bottom part anda top part. In this solution, the top part may comprise a top face andtwo intermediate parts intermediate the side faces and the top face, theintermediate parts being dismounted in the transported position and thetop face being arranged on the side faces of the bottom part in order tocover at least part of the space.

Thus, the top face can easily be arranged inside the width of the bottompart, and the intermediate parts can be placed within or outside thenacelle during transport.

The transportation height of the nacelle may be equal to or lower than 4metres, preferably 3.9 metres, more preferably 3.3 metres.

Thus, the maximum height of the nacelle during transport complies withthe maximum height for passing under bridges and through tunnels etc.specified by a number of European countries and in USA.

Moreover, the nacelle may further comprise a main frame structurearranged so that at least part of the top part can be supported by themain frame structure during transport.

The main frame structure may thus support the top part of the nacellewhen the top part extends inside the width of the bottom part of thenacelle.

In one embodiment, the main frame structure may comprise at least twosupport beams arranged along each side face.

Thus, the top part of the nacelle may be supported along itslongitudinal extension, preferably along its entire longitudinalextension.

In addition, the nacelle may comprise at least one connection part forconnecting the top part to the bottom part, the connection part beingsubstantially inside the nacelle in its installed position.

The connection part may be a detachable part so that it can be removedand used as support for at least part of the top part in the transportedposition.

The nacelle may moreover comprise a transport kit having transportationparts for enabling a cover of the space during transport.

In one embodiment, the transportation parts may be arranged partlyinside the nacelle during transport to provide a support of at leastpart of the top part.

Thus, if it is not possible to place the top part so that it covers thespace within the bottom part of the nacelle, the transportation partscan be used to prolong the top part to the sides and at the front andback ends, thus sealing off the space.

In a further embodiment, the transportation parts may comprise sealingmeans.

Thus, the transportation parts may facilitate a waterproof connectionbetween the top part and the main frame structure within the bottom partof the nacelle.

The nacelle may further comprise a plurality of rafters.

In one embodiment, some of the rafters may be adjustable in height.

When the height of the rafters is adjustable, the rafters can be used tosupport the top part during transport by lowering the height of therafters, thus also lowering the height of the nacelle.

In addition, the nacelle may further comprise detachable end faces.

When the end faces are detachable, they may be manufactured in onepiece, thus making them more rigid and adding greater stability to thenacelle. During transport, the detachable end faces may be placed insidethe nacelle, end to end with the nacelle, or askew so as to comply withthe requirements concerning maximum transportation height.

However, the detachable end faces may also be a part of the front orback ends of the nacelle.

In one embodiment, part of the intermediate part may overlap apredetermined part of the top face in the installed position whereas, inthe transported position, the intermediate part overlaps a lesser partof the top face than the predetermined part.

Thus, the top part can be prolonged to the sides during transport whilestill having sealing ability as the intermediate part and the top facestill overlap.

The invention also relates to a transport method for transporting anacelle as described above, the method comprising the step of placing atleast part of the top part in a transported position in which part ofthe top part overlaps part of the side faces of the bottom part.

In addition, the transport method may further comprise the step ofplacing intermediate parts and/or connection parts inside the space.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention and its many advantages will be described in more detailbelow with reference to the accompanying schematic drawings which, forthe purpose of illustration, show some non-limiting embodiments and inwhich

FIG. 1 shows a wind turbine nacelle according to the invention in itsinstalled position,

FIG. 2 shows the nacelle of FIG. 1 where the top part of the nacellecover has been dismounted,

FIG. 3 shows the nacelle of FIG. 1 in its transported position,

FIG. 4 shows a transportation kit,

FIG. 5 shows a cross-sectional view of the wind turbine nacelle in itstransported position,

FIG. 6 shows a sectional view of FIG. 5,

FIG. 7 shows a cross-sectional view of the wind turbine nacelle in itsinstalled position,

FIG. 8 shows a sectional view of FIG. 7,

FIG. 9 shows a sectional view of another embodiment of the wind turbinenacelle in its transported position,

FIG. 10 shows a sectional view of yet another embodiment of the windturbine nacelle in its installed position,

FIG. 11 shows a cross-sectional view of the wind turbine nacelle of FIG.10 in its transported position,

FIG. 12 shows a partly sectional view of the wind turbine nacelle,

FIG. 13 shows a cross-sectional view of yet another embodiment of thewind turbine nacelle in its installed position,

FIG. 14 shows a sectional view of the wind turbine nacelle of FIG. 13 inits transported position,

FIG. 15 a shows another embodiment of the nacelle in its alternativetransported position,

FIG. 15 b shows yet another embodiment of the nacelle in its alternativetransported position,

FIG. 16 shows a cross-sectional view of FIG. 15 a or 15 b through themiddle section of the nacelle in its installed position,

FIG. 17 shows a cross-sectional view of FIG. 15 b through the middlesection of the nacelle in its alternative transported position,

FIG. 18 shows another embodiment of the wind turbine nacelle in itstransported position,

FIG. 19 shows a cross-sectional view of FIG. 18 through the middlesection of the nacelle in its transported position,

FIG. 20 shows a cross-sectional view of FIG. 18,

FIG. 21 shows a sectional view of the main frame structure of theinvention,

FIG. 22 shows the structure of FIG. 21 in its folded position,

FIG. 23 shows another embodiment of the wind turbine nacelle in itstransported position,

FIG. 24 shows a cross-sectional view of FIG. 23,

FIG. 25 shows another embodiment of the wind turbine nacelle inperspective,

FIG. 26 shows the nacelle of FIG. 25 in its transported position,

FIG. 27 shows a cross-sectional view of the nacelle of FIG. 25 in itsinstalled position,

FIG. 28 shows a cross-sectional view of the nacelle of FIG. 25 in itstransported position,

FIG. 29 shows a cross-sectional view of another embodiment of thenacelle in its installed position,

FIG. 30 shows a cross-sectional view of the nacelle of FIG. 29 in itstransported position, and

FIGS. 31 and 32 show how the rafters can be minimised during transport.

All the drawings are schematic and not necessarily to scale, and theyshow only those parts necessary to elucidate the invention, other partsbeing omitted or merely suggested.

DETAILED DESCRIPTION OF THE INVENTION

A wind turbine nacelle is shown in FIG. 1. When a wind turbine nacelle 1is installed, the nacelle is positioned on a tower (not shown) andconnected to three rotor blades through a hub (not shown) in a front end8 of the nacelle. The hub with rotor blades is always turned to face thewind and the turning movement is performed in a yaw of the bottom of thewind turbine nacelle 1 in the connection with the tower. The nacelle 1is usually constructed having a main frame structure 12 comprising abottom frame extending from the yaw, which bottom frame supports thenacelle, the hub, and the rotor blades. The nacelle 1 has a cover 9 inorder to protect the interior parts of the nacelle, such as thegenerator, the gear, etc., which parts together is called the drivetrain 26. In this way, the weight of the nacelle, the hub, and the rotorblades is distributed by the bottom structure to the tower.

The cover 9 is fastened to the frame, typically to the bottom of theframe, and the cover is a self-supporting construction carrying its ownweight. When the nacelle 1 is assembled, it has a first height h1 whichis also its installation height h1. When transporting the nacelle 1 on avehicle, such as a truck bed 27, the maximum height of the nacelle mustnot exceed 3.3 metres in many of the European countries and in the USA.However, the nacelle may have a height of up to 4 metres if loaded ontoa special transportation system where the nacelle is lowered downbetween a rear truck bed and a front truck bed on a separatetransportation frame.

In order to comply with these restrictions, a prior art nacelle isseparated into a bottom and a top part when it is to be transported, andeach part is transported on a separate truck bed. Each part is coveredby a tarpaulin so that rain and dirt whirled around during transportdoes not enter the interior of the nacelle.

When transporting the wind turbine nacelle, the drive train may betransported separately or mounted within the nacelle. If the nacelleweighs too much, the drive train is transported separately.

In the solution of the present invention, the nacelle 1 has a bottompart 2, an end part, and a top part 6. The bottom part 2 has twoopposing side faces 4 and during transport the top part 6 and the endpart are separated from the bottom part and the top part is arrangedinside or outside the bottom part. The top part 6 may thus be positionedin a second position inside the bottom part 2 so that the overall heightof the nacelle is reduced to comply with the transport restrictions ine.g. Europe and USA. In addition, the top part 6 also at least partlycovers the bottom part 2 during transport, thus making a tarpaulinexpendable.

In one embodiment of the invention, the side faces 4 of the bottom part2 are bent somewhat outwards in order to receive the top part 6 betweenthe side faces. In another embodiment, the side faces 4 of the bottompart 2 are bent somewhat inwards so that the top part 6 extends on theoutside of the two side faces. In both embodiments, the top part 6 isused as a roof part during transport, covering the space 5 within thewind turbine nacelle 1. Furthermore, due to the fact that the top part 6in this way at least partly overlaps or extends within the bottom part2, the overall height of the nacelle 1 is reduced. Moreover, a secondtruck bed 27 is no longer needed.

The wind turbine nacelle 1 of FIG. 1 can be separated into a front part8, a back part 30, a bottom part 2, and a top part 6. The top part 6comprises a top face 7 and two intermediate parts 10. Before transport,the separated front part 8, back part, and intermediate parts 10 arepositioned inside the interior space 5 of the nacelle 1. Subsequently,the top face 7 is arranged on an internal main frame structure 12 so asto form the roof of the nacelle 1 and thus close off the interior of thenacelle as shown in FIG. 2. In another embodiment, the top face 7 issupported directly on the side faces 4 of the bottom part 2 instead ofon the main frame structure 12.

By dividing the top part 6 into several parts, the overall height of thenacelle 1 can be reduced during transport without reducing theinstallation height h1. As wind turbines are constructed still larger,the need for such a separable wind turbine nacelle 1 is increasing. Theheight h1 of the installed wind turbine nacelle 1 is determined by thedrive train 26 and the travelling crane operating above the drive train,which is used for maintenance and repair work. The travelling cranemoves back and forth on wheels rolling on rails or a support beam, suchas an I-profile, on top of the main frame structure 12.

As can be seen from FIG. 2, only a top part of the end of the nacelle 1is separated from the bottom part 2 during transport. In this way, thestability of the wind turbine nacelle 1 is maintained.

The top face 7 covers part of the nacelle 1. However, in order to closeor seal off the rest of the interior of the nacelle 1, a transportationkit 11 comprising different transportation parts 13 are arranged toclose or seal off the rest of the nacelle 1, as shown in FIG. 3. To sealoff the interior of the nacelle 1, the transportation parts 13 may beequipped with sealing means arranged along the edges of eachtransportation part.

In the embodiment of FIGS. 3 and 4, the transportation kit 11 comprisesfive transportation parts 13, i.e. a back portion 14, a front portion15, two side portions 16, and a top portion 17. These portions are shownin an exploded view in FIG. 4. The transportation parts 13 may also bemade of a sealing material so that separate sealing means isunnecessary, or the portions may be arranged so that water flows fromone transportation part onto another and away from the nacelle 1.

As can be seen in FIG. 4, the transportation kit parts 13 are made froma substantially rigid material so that each part can carry its ownweight. Due to the fact that the transportation parts 13 aresubstantially rigid compared to a prior art cover solution, such as atarpaulin, the transportation parts can be reused several times fortransport of several wind turbine nacelles. When one wind turbine hasbeen installed, the transportation kit 11 is sent back to themanufacturing plant and is mounted on a new wind turbine nacelle fortransportation of the new wind turbine nacelle.

The prior art tarpaulins could not be reused since they always sufferedtoo much damage during transport. Deploying the transportation kit 11instead, the kit can be reused and when the kit parts 13 are toodamaged, they may be granulated and remoulded into new kit parts. Inthis way, the material of the transportation parts 13 can be reused overand over again. The transportation parts 13 may be moulded or vacuumformed from any kind of plastic, such as PE, PUR, PET, ABS, etc.

In FIG. 5, the top face 7 is arranged in a supported position on a setof support beams 18, such as an I-profile. As can be seen from FIG. 6,the side portion 16 of the transportation kit 11 overlaps the side faces4 of the bottom part 2 at its outside. Also, the side portion 16overlaps the top face 7 at the underside of the top face 7. In order tosupport the top face 7, the transportation kit 11 may further comprise aconnection portion 19 serving as a prolongation of the support beam.

FIG. 7 shows the assembled top part 6 from within the space 5 of thenacelle 1. The top face 7 is supported on a connection part 20 whichagain is supported by rafters 21. The rafters 21 are arranged insupportive connection with the support beam 18 which is supported by themain frame structure 12. Thus, the connection part 20 and the rafters 21are placed in the inside of the wind turbine nacelle cover 9 and thusnot visible from outside the cover.

As can be seen from FIG. 8, which is a sectional view of FIG. 7, theintermediate part 10 overlaps the side face 4 and the top face 7 so thatwater can run from the top face along the outside of the intermediatepart and further onto the outside of the side face.

When the nacelle 1 of FIG. 7 has been prepared for transport, therafters 21 and the connection parts 20 are separated from the supportbeam 18 and placed inside the nacelle. The intermediate parts 10 arealso placed inside the space 5 of the nacelle, and the space is closedby arranging the top face 7 as a lid on the support beams 18 as shown inFIG. 6. As can be seen from FIG. 6, the connection part 20 is reused forsupporting the side portion 16 of the transportation kit 11 and the topface 7.

Another way of supporting a top face 7 is shown in FIG. 9, in which theconnection part 20 is also reused. However, no additional connectionportions 19 are needed since the connection part 20 is supporteddirectly on the support beam 18 for supporting the side face 16 of thetransportation kit 11 and the top face 7.

In one embodiment, the installation height h1 of the wind turbinenacelle 1 of FIG. 7 may be 3.9 metres whereas the height h2 of thenacelle in the corresponding transported position, shown in FIG. 5, isapproximately 3.3 metres. In this way, the height of the nacelle 1 canbe reduced 60 centimetres, which is enough for it to be allowed to betransported on one truck bed 27 instead of two. Hereby, thetransportation cost is reduced since two separate trucks are no longerneeded. Furthermore, by reusing the transportation parts 13, the presentinvention becomes even more cost-saving and environment-friendly.

The rafters 21 may have all sorts of designs depending on the complexityand the design of the nacelle 1. In FIG. 10, the rafter 21 is shownhaving an indentation 24 in one end where it rests on the support beam18. When having such an indentation 24, no additional fittings 22, suchas those shown in FIG. 8, are needed. In addition, the rafter 21 may, inits other end, have an indention for supporting the connection part 20,making the construction more reliable. In this embodiment, the supportbeam 18 rests directly on the main frame structure 12.

In FIG. 11, yet another embodiment of the nacelle 1 is shown in itstransported position. In this embodiment, the top face 7 rests on theside portions 16 of the kit 11. To support the side portion 16, aconnection part 20 is connected to the support beam 18 through a bracket23. The support beam 18 is arranged on top of the main frame structure12. Furthermore, the top face 7 has a cross-sectional profile enablingthe top face to be dismounted both from the outside and the inside ofthe wind turbine nacelle 1.

The transportation parts 13 may have sealing means. However, if the topface 7 overlaps the transportation parts 13, which again overlap theside faces 4 or other transportation parts, and so forth as shown inFIG. 11, a sealing connection is provided since water runs from the topface down onto the transportation part and further onto the side face oran additional transportation part.

When the wind turbine nacelle 1 is in its installed position, theconnection part 20 for supporting the top face 7 may hinder parts of thedrive train 26 from being removed in order to perform repair ormaintenance work. Thus, the connection part 20 may be provided withindentations or made as separate parts along the length of the top face7, thus making it possible to take out either parts of the drive trainor the entire drive train 26. This is illustrated in FIG. 12, in whichmountings 25 of the drive train can easily pass through the indentationof the connection part 20.

In FIG. 13, the top part 6 is dividable into three parts, i.e. a topface 7 and two intermediate parts 10. The intermediate parts 10 abut theside faces 4 of the bottom part 2 and are held in place between the topface 7 and a connection part 20 which may be some kind of profile, suchas an H-profile, I-profile, etc. The connection part 20 is supported byrafters 21. In its transported position, as shown in FIG. 14, atransportation part 13, 16 is supported directly on the support beam 18for supporting the top face 7 and overlapping the side face 4 of thebottom part 2. In this embodiment of the nacelle 1 in its transportedposition, the connection part 20 is not reused as a support part, but ismerely positioned inside the space 5 of the nacelle.

The top part 6 may be separated into three parts when transported, asshown in FIGS. 15 a and 15 b. The intermediate parts 10 are eitherplaced either outside the top face 7 and are also supported by thesupport beam 18 as shown in FIG. 15 a, or the parts may be placed insidethe nacelle 1 as shown in FIG. 15 b. The intermediate parts 10 may havea variety of designs. In FIG. 16, the intermediate part 10 is shown as aframe structure made of elongated sheets. The top face 7 is connectedwith a connection part 20, which is a fixed part of the top face and maybe made from a sealing and/or flexible material. Thus, the top face 7has a sealing connection to the support beam 18 when the top face issupported by the support beam, as shown in FIG. 17. Thus, rain and otherprecipitation will flow from the outside of the top face 7 and along thesupport beam 18 to the ends of the support beams. If a transportationkit 11 is used, the top face 7 may make a sealing connection to thetransportation parts 13 of the kit.

In order to uphold the intermediate parts 10 and thus the top face 7,the nacelle 1 comprises a connection part 20 in the form of rafters 21or beams 18. The rafters 21 or beams 18 have indentations to provide areliable connection to the intermediate parts 10.

As mentioned and as is illustrated in FIGS. 18 and 20, the top face 7may also be one part which is placed in between the side faces 4 of thebottom part 2, squeezing the top part in between the side faces and thussomewhat increasing the width of the bottom part.

In the installed position of the wind turbine nacelle 1, rafters 21 orconnection parts 20 are placed intermediate the support beam 18 and thetop part 6 in order to support the top part as shown in FIG. 19. In thetransported position of the nacelle 1, the top face 7 is supporteddirectly on the support beam 18 as illustrated in FIG. 20.

In one embodiment, part of the main frame structure 12 is foldable asshown in FIGS. 21 and 22. In this way, the height of nacelle 1 can bereduced even further if necessary.

In addition, the top part 6 may be dividable into two parts which isseparated when preparing the nacelle 1 for transport. The top part 6 isseparated along the middle of the top part in the longitudinalextension. The top part 6 may be separated along its centre line oralong a line displaced from its centre line, thus either separating itinto two equally sized parts or separating it into two parts ofdifferent sizes. The design of the top part 6 depends on theconstruction of the drive train 26 so that the two parts are supporteddirectly or indirectly in a simple manner in relation to the drivetrain.

In FIG. 23, the top part 6 is separated into two equal parts andarranged in an overlapping position so that the parts can be placedeasily within the space 5 of the bottom part 2. In FIG. 24, the two topparts are supported by the main frame structure 12 using some kind ofconnection parts 20 (not shown) and the two parts overlap each other atthe top. In the transported position, the top parts may be supported bythe support beam 18.

In FIG. 25, the top part 6 is separated into two differently sizedparts. As can be seen in FIG. 25, the top part 6 is separated into twoparts and arranged so as to extend outside of the width w of the bottompart 2 so that part of the top parts overlaps the side face 4, as shownin FIG. 26.

In another embodiment, the intermediate parts 10 of the top part 6overlap the top face 7 in the installed position as shown in FIG. 27.When the nacelle 1 is prepared for transport, the intermediate parts 10are pulled outwards towards the side faces 4 so that the intermediateparts extend over and overlap the outside of the side faces 4. In thisoverlapping position, the intermediate parts 10 still overlap the topface 7 and are supported on the support beam 18. Thus, the overlapbetween the top face 7 and the intermediate part 10 in FIG. 27 is largerthan the overlap between the top face and the intermediate part in FIG.28. The rafter 21 shown in FIG. 27 is positioned inside the space 5 whenthe nacelle 1 is transported. Thus, one part may overlap a predeterminedpart of another part.

In FIGS. 29 and 30, the intermediate part 10 and the rafter 21 of FIG.27 have been constructed as one part so that the intermediate part 10both has the strength of the rafter and also serves as the cover 9 ofthe wind turbine nacelle 1. The intermediate part 10 overlaps apredetermined part of the top face 7 in FIG. 29, which predeterminedpart is decreased in the corresponding transported position of FIG. 30.The intermediate part 10 is supported by the support beam 18, which alsoserves as rails for the travelling crane. When the top part 6 is dividedinto two overlapping parts as in FIGS. 27-30, a simple design of thenacelle 1 is provided since the construction does not have a lot ofdifferent additional supporting and/or connecting parts. In this way, noadditional parts are needed for changing the nacelle 1 from itstransported position to its installed position, and vice versa. Theintermediate part 10 may constitute an additional expense; however, noexpenses will be needed for any additional parts.

In another embodiment, the rafters 21 may be adjustable in height inorder to minimise the height of the nacelle 1 during transport as shownin FIGS. 31 and 32. Some of the rafters 21 may have a telescopicconstruction, or one part of a rafter may be movable in relation toanother part of the same rafter to be able to prolong or decrease thelength of each rafter.

In one embodiment, four rafters 21, two in each side, are madeadjustable. When transporting the nacelle 1, all rafters 21 other thanthe four adjustable rafters are positioned inside the nacelle, and thefour adjustable rafters are reduced in height in order to comply withthe height restrictions for transports on ground.

In the embodiments of FIGS. 1-4, 15, 18, and 23, at least part of thefront part 8 of the nacelle is removed in order to fold the nacelle intoits transported position and thus decrease the height of the nacelle.

In the embodiments of FIG. 25-30, the nacelle 1 does not have adetachable front part 8, but the back part still has to be removed. Inanother embodiment, it is the front part 8 which is removed whenpreparing the nacelle for transport, whereas the back part of thenacelle is not detachable.

By a front part 8 and a back part is meant any kinds of detachable endfaces.

By a wind turbine is meant any kind of apparatus able to convert windpower into electricity, such as a wind generator, wind power unit (WPU),or wind energy converter (WEC). And by a wind turbine nacelle 1 is meantany kind of housing housing the drive train 26 of the wind turbine, e.g.the generator, the gear, etc.

Although the invention has been described above in connection withpreferred embodiments of the invention, it will be evident for a personskilled in the art that several modifications are conceivable withoutdeparting from the invention as defined by the following claims.

1. A nacelle for a wind turbine, the nacelle having a first height inits installed position and a second height in a transported position,the first height being greater than the second height, comprising: amain frame structure, a bottom part connected to the main framestructure and having a bottom face and two opposite side faces defininga space and a width of the bottom part and a top part, wherein when thenacelle is in the transported position, the top part extends inside thewidth of the bottom part, or outside the width of the bottom part, inorder to cover at least part of the space.
 2. The nacelle according toclaim 1, wherein the top part comprises two parts, and wherein the twoparts of the top part are separated from each other in the transportedposition of the nacelle in order for the top part to extend outside thewidth of the nacelle or overlap each other in the transported positionof the nacelle in order for the top part to extend inside the width ofthe nacelle.
 3. The nacelle according to claim 1, wherein the top partcomprises a top face and two intermediate parts intermediate the sidefaces and the top face, wherein the two intermediate parts aredismounted in the transported position.
 4. The nacelle according toclaim 1, wherein the top part comprises a top face and two intermediateparts intermediate the side faces and the top face, the intermediateparts being dismounted in the transported position and the top facebeing arranged on the side faces of the bottom part in order to cover atleast part of the space.
 5. The nacelle according to claim 1, whereinthe transportation height is equal to or lower than 4 m, preferably 3.9m, more preferably 3.3 m.
 6. The nacelle according to claim 1, furthercomprising the main frame structure arranged so that at least part ofthe top part is supported by the main frame structure during transport.7. The nacelle according to claim 6, wherein the main frame structurecomprises at least two support beams arranged along each side face. 8.The nacelle according to claim 1, further comprising at least oneconnection part for connecting the top part to the bottom part, theconnection part being substantially inside the nacelle in the installedposition.
 9. The nacelle according to claim 8, wherein the connectionpart is used as support for at least part of the top part in thetransported position.
 10. The nacelle according to claim 1, furthercomprising a transport kit having transportation parts for enabling acover of the space during transport.
 11. The nacelle according to claim10, wherein the transportation parts are arranged inside the nacelleduring transport to provide a support of at least part of the top part.12. The nacelle according to claim 10, wherein the transportation partscomprise sealing means.
 13. The nacelle according to claim 1, furthercomprising a plurality of rafters.
 14. The nacelle according to claim13, wherein at least some of the rafters are adjustable in height. 15.The nacelle according to claim 1, further comprising detachable endfaces.
 16. The nacelle according to claim 1, wherein part of theintermediate part overlaps a predetermined part of the top face in theinstalled position whereas, in the transported position, theintermediate part overlaps a lesser part of the top face than thepredetermined part.
 17. A transportation kit according to claim
 10. 18.A transport method for transporting a nacelle according to claim 1, themethod comprising the step of placing at least part of the top part in atransported position in which part of the top part overlaps part of theside faces of the bottom part.
 19. The transport method according toclaim 18, further comprising the step of placing intermediate partsand/or connection parts inside the space.